
package com.newki.glrecordx.camerax.filters.gpuFilters.paramsFilter

import android.opengl.GLES20
import com.newki.glrecordx.camerax.filters.gpuFilters.baseFilter.GPUImageFilter

class GPUImageHueFilter constructor(private var mHue: Float = 1.5f) : GPUImageFilter(
    NO_FILTER_VERTEX_SHADER, HUE_FRAGMENT_SHADER
) {
    private var mHueLocation = 0
    public override fun onInit() {
        super.onInit()
        mHueLocation = GLES20.glGetUniformLocation(program, "hueAdjust")
    }

    public override fun onInitialized() {
        super.onInitialized()
        setHue(mHue)
    }

    fun setHue(hue: Float) {
        mHue = hue
        val hueAdjust = mHue % 360.0f * Math.PI.toFloat() / 180.0f
        setFloat(mHueLocation, hueAdjust)
    }

    companion object {
        const val HUE_FRAGMENT_SHADER = "" +
                "precision highp float;\n" +
                "varying highp vec2 textureCoordinate;\n" +
                "\n" +
                "uniform sampler2D inputImageTexture;\n" +
                "uniform mediump float hueAdjust;\n" +
                "const highp vec4 kRGBToYPrime = vec4 (0.299, 0.587, 0.114, 0.0);\n" +
                "const highp vec4 kRGBToI = vec4 (0.595716, -0.274453, -0.321263, 0.0);\n" +
                "const highp vec4 kRGBToQ = vec4 (0.211456, -0.522591, 0.31135, 0.0);\n" +
                "\n" +
                "const highp vec4 kYIQToR = vec4 (1.0, 0.9563, 0.6210, 0.0);\n" +
                "const highp vec4 kYIQToG = vec4 (1.0, -0.2721, -0.6474, 0.0);\n" +
                "const highp vec4 kYIQToB = vec4 (1.0, -1.1070, 1.7046, 0.0);\n" +
                "\n" +
                "void main ()\n" +
                "{\n" +
                "    // Sample the input pixel\n" +
                "    highp vec4 color = texture2D(inputImageTexture, textureCoordinate);\n" +
                "\n" +
                "    // Convert to YIQ\n" +
                "    highp float YPrime = dot (color, kRGBToYPrime);\n" +
                "    highp float I = dot (color, kRGBToI);\n" +
                "    highp float Q = dot (color, kRGBToQ);\n" +
                "\n" +
                "    // Calculate the hue and chroma\n" +
                "    highp float hue = atan (Q, I);\n" +
                "    highp float chroma = sqrt (I * I + Q * Q);\n" +
                "\n" +
                "    // Make the user's adjustments\n" +
                "    hue += (-hueAdjust); //why negative rotation?\n" +
                "\n" +
                "    // Convert back to YIQ\n" +
                "    Q = chroma * sin (hue);\n" +
                "    I = chroma * cos (hue);\n" +
                "\n" +
                "    // Convert back to RGB\n" +
                "    highp vec4 yIQ = vec4 (YPrime, I, Q, 0.0);\n" +
                "    color.r = dot (yIQ, kYIQToR);\n" +
                "    color.g = dot (yIQ, kYIQToG);\n" +
                "    color.b = dot (yIQ, kYIQToB);\n" +
                "\n" +
                "    // Save the result\n" +
                "    gl_FragColor = color;\n" +
                "}\n"
    }
}